Binder based on natural hydraulic lime for concrete and mortar consisting of vegetable aggregates

Abstract

The present invention relates to a new composition of environmentally friendly hydraulic binder for plant-based aggregate materials, such as hempcrete. The composition incorporates a very high content of natural hydraulic lime while ensuring optimal mechanical properties. In particular, the invention proposes to optimize mechanical performance through the use of a mixture of calcium sulfate and aluminous cement. The setting and hardening times of the materials are also significantly reduced, thus accelerating the production of plant-based aggregate materials.

Description

TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to the field of binders for concrete, mortar, and plaster based on plant aggregates. More particularly, the invention relates to a binder based on natural hydraulic lime for concrete or plaster made from hemp or any other plant aggregate.

[0002] The invention finds particular application in the manufacture of hemp concrete, prefabricated or applied by formwork and projection. STATE OF THE ART

[0003] Hempcrete is an ecological and sustainable building material. It is made by mixing hemp shives (the woody part of the hemp stalk) with a binder, usually lime, natural cement, or clay. This mixture creates a thermally and acoustically insulating, as well as breathable, material. Materials with similar characteristics can also be made with other plant-based aggregates such as wood chips, flax shives, miscanthus, coconut fibers, etc.

[0004] While hempcrete offers numerous advantages, it also presents some specific challenges in its use. For example, its drying time is quite long and can generate additional delays and constraints in the construction process. It is also essential to pay attention to the mechanical properties of the mix, which are weakened in the presence of hemp, as well as any other plant-based aggregate. Therefore, it is important to verify the mechanical strength, setting time, and hardening kinetics of these materials.

[0005] The composition of binders for hempcrete is a crucial aspect that influences the mechanical, thermal, and environmental properties of the final material. From an ecological perspective, the quantities of Portland cement or hydraulic lime (HL) (which may contain cement) must be limited. Ideally, binders for hempcrete are natural materials that integrate well with hemp, such as natural hydraulic lime (NHL) or clay. However, these binders do not guarantee sufficient early-age mechanical strength for hempcrete in all applications.

[0006] International patent application WO 2015 / 082513 A1 provides examples of concretes and mortars made from plant-based materials containing air lime. It addresses the problem of the hydrophilic nature of plant aggregates, which results in increased water requirements in the mixtures and longer setting and drying times. It also mentions that plant aggregates release organic molecules that interact undesirably with the mineral binder, thus delaying its setting. This document proposes optimized binder formulas to mitigate the undesirable effects of plant aggregates. These compositions are based on air lime with an increased specific surface area, incorporating approximately 40% Portland cement.

[0007] International patent application WO 03 / 004435 also deals with hemp concrete and mortar, and proposes binder compositions comprising 50 to 80% by mass of air lime, and 10 to 70% of a hydraulic binder such as cement and hydraulic lime, and optionally 5 to 10% by weight of pozzolanic fillers such as volcanic ash. In particular, the compositions are optimized to allow the air lime to dry and set. The compositions are also optimized to mitigate the drawbacks of water release by the organic matter. To this end, the compositions also include a pore-forming and capillary-forming agent to help wick water to the surface of the material. Furthermore, it is also suggested that a water-repellent additive or a surfactant be added to limit the reabsorption of moisture by the hemp.However, this document provides no specific examples of composition nor does it specify the drying time of these compositions. A significant cement content is assumed for the manufacture of materials that guarantee good mechanical performance.

[0008] However, the production of Portland cement is energy-intensive and generates significant carbon dioxide emissions. The use of Portland cement is therefore deplorable in an eco-material, and its presence in binder compositions should be reduced as much as possible without compromising their mechanical performance. Furthermore, its presence imparts an unnatural, concrete-grey color.

[0009] Patent application EP 2 263985 A1 describes a binder for a hemp-based composite building material. This binder is formulated with hydraulic lime and metakaolin. The formula also incorporates additives such as a shrinkage-reducing, water-repellent hardener like glycerol carbonate, and / or an air-entraining agent. A composite material exhibiting good mechanical strength can be obtained when this binder is mixed with hemp granules at a concentration of 15 to 30% by dry mass of the binder, with a water-to-binder ratio of 0.5 to 1.5. These compositions do not contain Portland cement and exhibit good mechanical properties. However, the setting and drying times of these compositions can be further optimized. SUMMARY OF THE INVENTION

[0010] This concerns a new ecological binder composition with a high content of natural hydraulic lime for the preparation of materials for concretes and mortars of plant aggregates.

[0011] The invention notably proposes a hydraulic binder composition for concretes or mortars made from plant-based aggregates, comprising: a first part called "A" of hydraulic binder comprising by dry mass at least 75% natural hydraulic lime by total weight of said part A, preferably at least 85% natural hydraulic lime, and a second part called "B" consisting of a mixture of calcium sulfate and aluminous cement, and in which part A of hydraulic binder represents at least 70% by dry mass on a total weight of the binder composition.

[0012] This composition yields an environmentally friendly binder with a very high concentration of natural hydraulic lime, while guaranteeing good mechanical strength at both early and long-term ages, as well as a natural visual appearance. Indeed, component B of the composition allows for control of the mechanical properties of the binder and the plant-based aggregate materials without necessarily requiring the use of Portland cement, and without the need for additives or additional treatments to compensate for the release of water and other molecules by the plant-based aggregates.

[0013] Advantageously, the mass ratio "A / B" in the composition is between 2.3 and 8, preferably between 4 and 6. This ratio optimizes the mechanical properties of a composition with a high content of natural hydraulic lime. Preferably, the total mass concentration of Portland cement in the binder composition is ≤ 10%, preferably ≤ 5%. Preferably, the cement will conform to standard NF EN 197-1 and will be selected from cements of class CEM I 52.5 N or CEM I 52.5 R.

[0014] Another objective of the invention is to optimize the setting and drying time of plant aggregate materials made with the hydraulic binder of the invention.

[0015] To this end, the invention proposes to adjust a mass ratio of calcium sulfate / aluminous cement in the composition from 0.3 to 0.7.

[0016] The invention also proposes to include an accelerator in the composition, chosen from an alkali metal salt such as lithium carbonate, lithium sulfate, sodium carbonate, sodium sulfate, potassium sulfate, and potassium carbonate. This improves the setting and hardening time.

[0017] Similarly, the combination of the setting accelerator and the mass ratio of calcium sulfate to aluminous cement ensures a setting time of less than 16 hours and hardening sufficient for the prefabrication of hempcrete components and demolding in less than 24 hours, even at low temperatures (below 10°C and above or equal to 5°C). The setting accelerator will be present at a concentration of 0.05 to 2% by dry mass of the total weight of the composition, preferably 0.1 to 1%. In a preferred embodiment, the setting accelerator is sodium sulfate, which is very effective at low concentrations, particularly from 0.1% or 0.2%, according to tests performed.

[0018] Preferably, part A of the composition consists, by dry mass, of at least 85% natural hydraulic lime and 0 to 15% Portland cement by the total weight of said part A, and preferably of at least 90% natural hydraulic lime and 0 to 10% Portland cement.

[0019] The composition of the hydraulic binder can be formulated with the following characteristics: Part A consists of at least 90% natural hydraulic lime by dry mass, and 0 to 10% Portland cement by the total dry mass weight of said first part, and preferably represents at least 80% by dry mass by the total weight of the binder composition, in Part B consisting of the mixture of calcium sulfate and aluminous cement, the aluminous cement being chosen from a calcium aluminate cement CAC, a sulfo-aluminate cement CSA or a mixture of the latter, and in which composition a mass ratio A / B is between 4 and 8, preferably between 4 and 6 and a mass ratio of calcium sulfate / aluminous cement is between 0.3 and 0.7, and said composition includes an accelerating adjuvant of the type "alkaline metallic salt".

[0020] In the preparation of the hydraulic binder, the composition of the invention is mixed with water in a mass ratio of 0.5 to 1.5, preferably 1 to 1.5.

[0021] The invention also relates to a composition of concrete, mortar or coating, comprising a hydraulic binder composition according to the invention and vegetable aggregates, such as hemp, flax, miscanthus and rapeseed aggregates.

[0022] Finally, the invention relates to a method for manufacturing a composite material, comprising: a step of preparing a binder composition according to any one of claims 1 to 8 mixed with water in a mass ratio of 0.5 to 1.5, and incorporating 15 to 80% by weight of a plant aggregate relative to the dry mass of the binder composition.

[0023] Other features and advantages of the invention will become apparent from the following detailed description of a non-limiting example of an embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] The present invention relates to a new binder based on natural hydraulic lime for plant-aggregate concretes such as hempcrete. "Plant-aggregate concretes" are broadly defined as any concrete, mortar, or plaster incorporating a plant-based aggregate such as hemp shives, flax, miscanthus, rapeseed, coconut fibers, etc. The binder of the invention is intended for use in the preparation of plant-aggregate concretes applied by formwork, dry spraying, or for the manufacture of components, such as blocks or insulating panels, by molding.

[0025] Natural hydraulic lime (NHL) is a lime with hydraulic properties produced by calcining limestone, which may or may not contain clay or silica, and reducing it to a powder by slaking, with or without grinding. It contains no added materials and sets and hardens when mixed with water, and through reaction with carbon dioxide in the air (carbonation). Natural hydraulic lime is classified into different categories based on its strength. Common classifications include NHL 2, NHL 3.5, and NHL 5, where the number indicates the minimum compressive strength after 28 days as defined by EN 459-1.

[0026] In comparison, hydraulic lime (HL) is a binder composed of lime and other materials such as cement, blast furnace slag, fly ash, limestone filler, and other suitable materials. Lime can be either air lime (CL; it hardens under the influence of carbon dioxide) or hydraulic lime (NHL), and the proportions of these materials can vary considerably, sometimes to very low levels. Indeed, hydraulic lime (HL) compositions can incorporate up to 50% Portland cement by mass, which significantly increases the binder's mechanical performance. Hydraulic lime (HL) compositions do not guarantee an environmentally friendly material.

[0027] A first objective of the invention is therefore to provide a true binder composition with a high content of natural hydraulic lime, and a reduced content of Portland cement, while guaranteeing optimal performance in terms of mechanical resistance in relation to the applications concerned.

[0028] A second objective of the invention is that the binder ensures a faster setting and hardening time for hempcrete than existing formulas. In particular, it is desired that this binder will allow the industrial production of prefabricated plant-aggregate concrete components that can be demolded or repositioned after 16 hours of setting (example: insulating hempcrete panels or blocks).

[0029] A third objective of the invention is to ensure the composition is easy to implement. It is also desirable to minimize the carbon footprint of the binder.

[0030] For these purposes, the invention proposes a binder composition with a high content of natural hydraulic lime, and whose mechanical and hardening properties can be controlled by its combination with a mixture of aluminous cement and calcium sulfate.

[0031] More specifically, the invention proposes a hydraulic binder composition for concretes or mortars made from plant-based aggregates, comprising: a) A first part, referred to as "A", of hydraulic binder comprising, by dry mass, at least 75% natural hydraulic lime (NHL) conforming to standard NF EN 459-1, preferably at least 85% natural hydraulic lime by total weight of said part A, and b) A second part, referred to as "B", consisting of a mixture of calcium sulfate and aluminous cement

[0032] Advantageously, this mixture allows for the formulation of binders with a very high content of natural hydraulic lime, and a highly desirable visual appearance due to its natural color, while also providing good mechanical performance when mixed with plant-based aggregates. The use of Portland cement can thus be significantly reduced, or even eliminated, and the binder's carbon footprint is therefore considerably lowered.

[0033] Part A forms the basis of the composition and represents at least 70% of the total dry weight of the binder composition. Part A is primarily composed of natural hydraulic lime, possibly mixed with Portland cement to enhance mechanical strength. However, the addition of a mixture of calcium sulfate and aluminous cement (Part B) allows for compositions without Portland cement, while maintaining optimal mechanical properties.

[0034] Part B will be incorporated into the composition at a mass ratio A / B of 2.3 to 8, preferably 3 to 6, to achieve the highest mechanical strength in the absence of Portland cement or at very low concentrations. In preferred embodiments, the total mass concentration of Portland cement in the binder composition is ≤ 5%.

[0035] The aluminous cement is chosen from calcium aluminate cement "CAC" and sulfo-aluminous cement "CSA". Mixtures of these can also be used.

[0036] CAC or CSA reacts with calcium sulfate, and with calcium dihydroxide and the C₂S of natural hydraulic lime to form ettringite (C₆A₃H₃₂) and stratlingite (C₂A₃H₃₂), respectively. In the present invention, the addition of calcium sulfate is necessary to optimize the reaction with aluminous cement. In particular, a mass ratio of calcium sulfate to aluminous cement in part B is between 0.3 and 0.7. The main advantages are rapid setting time and strength development. Their use also reduces the action of soluble (water-soluble) hemp species, which act as setting retarders and negatively impact the hydration of the binder compounds.

[0037] The choice of aluminous cement type, its specific content, and its ratio to calcium sulfate will depend on the desired compressive strength, the final application (plaster, mortar, or concrete), its mixture with plant or mineral aggregates, and the dimensions of the materials to be manufactured. For example, since CSA naturally contains calcium sulfate, the mass ratio of calcium sulfate to aluminous cement in section B can be lower. However, the addition of calcium sulfate is necessary to provide a free, more reactive source of calcium sulfate and optimize the reaction with the CSA.

[0038] As previously mentioned, the binder of the invention comprises a majority base of natural hydraulic lime, which is included in part A of the composition. According to a preferred embodiment, part A comprises or is made up of 90 to 100% natural hydraulic lime and 0 to 10% Portland cement by dry mass, based on the total weight of said part A.

[0039] The hydraulic lime in Part A is a natural hydraulic lime, such as NHL 2, NHL 3.5 and NHL 5. In a preferred embodiment of the composition, the hydraulic lime is NHL 3.5 and NHL 5.

[0040] The composition may also include one or more additives, notably a setting accelerator, to ensure rapid setting and hardening. Preferably, the accelerator is chosen from an alkaline salt such as lithium carbonate, lithium sulfate, sodium carbonate, sodium sulfate, potassium sulfate, or potassium carbonate. The setting accelerator is present at a concentration of 0 to 2% by dry mass of the total weight of the composition, and preferably from 0.1% to 1%. The use of the setting accelerator ensures rapid setting in all compositions, as well as the demolding of hempcrete pieces as early as 4 p.m.

[0041] Advantageously, the invention proposes using sodium sulfate as a setting accelerator. Sodium sulfate makes it possible to replace the use of lithium carbonate as an effective setting accelerator in this type of composition, and thus improve the ecological footprint and health impact of the binder composition. In another embodiment, a setting accelerator is added to the composition during the mixing of the binder composition with water for the preparation of plant-aggregate concrete.

[0042] In general, the compositions exhibit very good application properties and do not require a retarder. Of course, additional admixtures can also be used. For example, the composition may include a retarder such as citric acid and a retainer such as cellulose ether. These admixtures are particularly useful when the binder is mixed with a low proportion of water and / or when using sulfoaluminate cements. This allows for easier placement of the compositions, and the initial setting time can be slightly delayed. The retarder and retainer admixtures will be present at a concentration of 0.01% to 1% by mass on a dry weight basis of binder, preferably 0.05% to 0.2%.

[0043] According to preferred embodiments, the compositions of the invention incorporate, by dry mass relative to the total weight of the composition, at least 70% natural hydraulic lime, and preferably at least 75%, 80%, or 85% natural hydraulic lime and 0 to 30% Portland cement. The binder of the composition is therefore essentially composed of natural hydraulic lime mixed with calcium sulfate and aluminous cement. Indeed, this composition is effective with a very low concentration of additives, in particular a setting accelerator at a concentration of at least 0.1% in the composition.

[0044] The compositions of the invention thus guarantee the obtaining of a homogeneous mixture of plant-based aggregate concrete, prepared beforehand for manual application or by spraying. In the latter case, the binder mixed with water is kept in a separate container and mixed with the hemp aggregates at the time of spraying. Similarly, it will be possible to overcome the undesirable effects of using plant-based aggregates (delayed setting and reduced mechanical properties). Rapid setting of these materials is guaranteed even at low temperatures.

[0045] Advantageously, the compositions of the invention make it possible to increase the production rate of hempcrete components, such as blocks and panels for wall insulation. For example, these elements can be demolded or repositioned more quickly during drying. Similarly, the time required for any construction process involving these materials can be optimized by the binder of the invention.

[0046] Finally, the hardening properties of the compositions of the invention allow the prefabricated hempcrete walls to be erected without collapse. Furthermore, the compositions do not require a retarder and can be easily applied without problems of unwanted drying or sticking to tools. EXPERIMENTAL SECTION 1. Mixing the binder with hemp and manufacturing the hempcrete test specimens

[0047] In a cement mixer, introduce the water (30-35L) and the binder (18-25 kg), let it mix for 3 to 5 minutes then add the hemp (100L) and let it knead to obtain a homogeneous mixture.

[0048] Cylindrical molds measuring 16 x 32 cm are filled by applying three layers of mortar, compacted manually using a 16 cm wide tamper. After filling, the resulting test specimens are covered with a plastic lid to limit drying by contact with air.

[0049] The test specimens are kept at a temperature of 20°C and a relative humidity of 50%. This environmental control helps to guarantee constant conditions during the mortar hardening period, thus ensuring the reliability of the experimental results. 2. Characterization 2.1 Characterization at 4 p.m.: validation of the possibility of demolding the test specimens

[0050] Checking the hardness of the test specimen and the possibility of demolding and retaining the shape. 2.2 Characterization at 14 days: verification of short-term mechanical performance

[0051] Performing a compression resistance test (Rc 14j). Demolding the specimens without breaking them in two. 2.3 Characterization at 90 days: verification of long-term mechanical performance 2.4 Performing compression resistance tests (Rc 90j).

[0052] These methodical steps provide a complete evaluation of the mortar's properties, from setting time to compressive strength at different time points. 3. Results

[0053] Tables 1 and 2 below show examples of binder formulas and their characterization in tests with hemp. The results in Table 1 were obtained with binder formulas according to the invention, while Table 2 shows comparative tests with binder formulas not conforming to the invention. All formulas 1 to 12 consist of a mixture of part A and part B to which sodium sulfate is added as a setting accelerator. The percentages of each component of part A and part B are given as a percentage by dry mass relative to the weight of said part A and B, respectively. Formula 10 contains neither part B nor a setting accelerator. Formula 12 does not contain a setting accelerator. The concentration of sodium sulfate is expressed as a percentage by dry mass relative to the total weight of the binder composition. Formula 13 does not contain calcium sulfate. Table 1 - Characteristics of hemp concrete test specimens with conforming mechanical properties, of which formulas 4 to 9 are formulas according to the invention. binder composition Formula No. 1 2 3 4 5 6 7 8 9 Part A Portland Cement (%) 41,9 36,8 38,9 5,9 NHL 5 (%) 100 94,1 100 100 100 NHL 3.5 (%) 58,1 63,2 61,1 100 Part B Calcium Aluminate Cement (CAC) % 75,0 66,7 60,0 60,0 60,0 66,7 66,7 CSA (%) 60,0 60,0 Calcium sulfate (C$) 25,0 33,3 40,0 40,0 40,0 33,3 33,3 40,0 40,0 Mass ratio C$ / CAC or CSA 0,33 0,5 0,67 0,67 0,67 0,5 0,5 0,67 0,67 Mass ratio A / B 2,6 4 3,4 4,7 5,7 5,7 4,8 6,7 7,9 Sodium sulfate % 0,4 0,4 0,4 0,2 0,2 0,2 0,2 0,2 0,2 Hemp concrete Target Result Performance Unmolding at 4pm Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Demolding at 14 days Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Rc 14j (MPa) >1 1 1 1 Rc 90j (MPa) >1,2 1,5 1,5 1,7 1,2 1,2 1,2 1,2 1,4 1,2

[0054] As demonstrated in the tests, mixing part A with part B optimizes the mechanical performance of hempcrete materials in the absence of Portland cement (formulas 4, 5, and 7 to 9), or at very low concentrations (formula 6). Mechanical performance is particularly optimized with a mass ratio A / B of 2.6 to 8. A mass ratio A / B of 4 to 6 is preferred when the formula contains at least 80% NHL by total dry mass, supplemented primarily with the CAC / C$ mixture. Similarly, the ability to demold the parts after 16 hours shows that a mass ratio C$ / CAC or CSA of 0.3 to 0.7 optimizes the setting and hardening time of the materials, especially in the presence of a setting accelerator, preferably with a concentration of 0.5 to 0.7. Table 2- Characteristics of hemp concrete test specimens obtained with binder formulas not conforming to the invention. binder composition Formula No. 10 11 12 13 Part A Portland Cement (%) 53,0 33,7 41,8 68.3 NHL 5 (%) NHL 3.5 (%) 47,0 66,3 58,2 31.7 Part B Calcium Aluminate Cement (CAC) % 59,6 75,0 CSA (%) 100 Calcium sulfate (C$) 40,4 25,0 C$ / CAC or CSA 0,68 0,33 Ratio A / B 8,2 2,6 2,43 Sodium sulfate 0,2 0.44 Hemp concrete Target Result Performance Unmolding at 4pm Yes No No No No Demolding at 14 days Yes Yes No Yes No Rc 14j (MPa) >1 1 - Rc 90j (MPa) >1,2 1,2 -

[0055] Example 10 shows the effect of the absence of component B in a binder composition; this prevents the rapid setting and hardening of hempcrete materials. However, the mechanical performance is ensured by the high concentration of Portland cement. Formula 11 demonstrates the importance of the A / B mass ratio for achieving satisfactory early-age mechanical properties and rapid setting and hardening (demolding at 16 hours). For this last formula, the mechanical performance develops too slowly, and the composition is rejected. Example 12 shows the effect of the absence of sodium sulfate as a setting accelerator. Example 13 shows the effect of the absence of calcium sulfate.Even when using a sulfo-aluminate cement (CSA) as the source of aluminate cement, and with a relatively high sodium sulfate content, the absence of a complementary addition of calcium sulfate is detrimental to demolding at 16h or 14d.

Claims

1. Composition of hydraulic binder for concretes or mortars of vegetable aggregates comprising: - a first part called "A" of hydraulic binder comprising by dry mass at least 75% of natural hydraulic lime by a total weight of said part A, and - a second part called "B" consisting of a mixture of calcium sulfate and aluminous cement, and in which part A represents at least 70% by dry mass by a total weight of the binder composition.

2. Hydraulic binder composition according to claim 1, wherein a mass ratio "A / B" is between 2.3 and 8.

3. Hydraulic binder composition according to claim 2, wherein a mass ratio "A / B" is between 4 and 6.

4. Hydraulic binder composition according to any one of the preceding claims, wherein a mass ratio of calcium sulfate / aluminous cement in part B is between 0.3 and 0.

7.

5. Hydraulic binder composition according to any one of the preceding claims, wherein the composition comprises a setting accelerator adjuvant selected from an alkali metal salt such as lithium carbonate, lithium sulfate, sodium carbonate, sodium sulfate, potassium sulfate, and potassium carbonate.

6. Hydraulic binder composition according to claim 5, wherein the setting accelerator is sodium sulfate.

7. Hydraulic binder composition according to any one of the preceding claims, wherein part A consists by dry mass of at least 85% natural hydraulic lime and 0 to 15% Portland cement by total weight of said part A, and preferably of at least 90% natural hydraulic lime and 0 to 10% Portland cement.

8. Hydraulic binder composition according to claim 1, wherein - part A consists by dry mass of at least 90% natural hydraulic lime, and 0 to 10% Portland cement by the total dry mass weight of said first part, and preferably represents at least 80% by dry mass by the total weight of the binder composition, - in part B consisting of the mixture of calcium sulfate and aluminous cement, the aluminous cement being selected from calcium aluminate cement (CAC), sulfoaluminate cement (CSA) or a mixture thereof, and wherein the mass ratio A / B is between 4 and 8, preferably between 4 and 6, and the mass ratio of calcium sulfate / aluminous cement is between 0.3 and 0.7, and said composition comprises a setting accelerator selected from an alkali metal salt.

9. Hydraulic binder composition according to any one of the preceding claims, wherein the natural hydraulic lime is selected from NHL3.5, NHL 5 or a mixture thereof.

10. Binder composition according to any one of the preceding claims, said binder being mixed with water in a mass ratio of 0.5 to 1.5, preferably 1 to 1.

5.

11. Concrete, mortar or plaster composition comprising a hydraulic binder composition according to any one of the preceding claims and vegetable aggregates, such as hemp, flax, miscanthus and rapeseed aggregates.

12. Method for manufacturing a composite material, comprising: - a step of preparing a binder composition according to one of claims 1 to 9 mixed with water in a mass ratio of 0.5 to 1.5, and incorporating from 15 to 80% by mass of a vegetable granulate relative to the total dry mass of the binder composition.

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